I just installed my wrxpower uppipe. Did it from below (without removing the Turbo) Took me 11 hours by myself (including setup, cleanup, and 2 trips to hardware store for 14mm wrench and sockets). If I had jacked up the engine a bit, I would have saved 2 hours fiddling with trying to remove the old uppipe. On the positive side, I didn't lose any oil or anti-freeze from removing the Turbo. I also had 0 stripped or siezed nuts, bolts, or studs.
It does feel like it's making a little more power, so I would guess about a 10HP increase. There have been dyno plots that confirm this, but I haven't dyno'd my car yet. However the noticeable differences are better throttle response and faster turbo spool up with less lag.
Smokin! Tightened up the bolts on the downpipe thinking there might be a leak and took it out for a spin. The car started smokin real bad. Pulled over to check it out, and noticed it was power steering fluid that was smoking. Turns out, the compression fitting on the power steering line was way loose and after jacking up the engine, it started leaking PS fluid onto the downpipe. Had to tighten up the compression fitting and put in more PS fluid. It seems all good now, but It still makes a whistling sound at high RPM's and full throttle. Thinking it may just sound that way now because I cant find any leaks when doing a check around the fittings with my hand while the car is running. Maybe I need to check while under full boost at 6-7K as this is the only time it makes that noise.